The “cross between Concorde, a rail gun and an air hockey table” will deliver passengers between US cities faster than the speed of sound.

The history of transport is replete with dreamers who have concocted such schemes for getting people from A to B in previously unimagined haste. And many of them have remained just that, impractical ideas on a drawing board that will never see the light of day.

The Hyperloop: the pneumatic travel route faster than the speed of sound

But the latest mysterious project, which has had the technology world buzzing for months, has one crucial difference. Its backer is a Silicon Valley wunderkind with a proven track record of turning science fiction into reality.

Billionaire Elon Musk’s CV is impressive, to say the least. He made his initial fortune from PayPal, the online secure payment system, before going on to launch spaceships. Last year his SpaceX venture became the first private operation to dock a cargo capsule with the International Space Station.

Elon Musk (Getty Images)

Back on Earth, Mr Musk also founded Tesla, which has made electric sports cars viable and profitable.

Robert Downey Jr's portrayal of Tony Stark, the mercurial multi-millionaire alter ego of Iron Man in the Marvel superhero films, is reputedly based on him.

So when Mr Musk, 42, announced that he would be publishing plans for the Hyperloop on Monday, August 12 - tomorrow - scientists were sent into a tailspin.

They will have to wait for Mr Musk to post his “alpha design” on the internet then but he has dropped several hints about its features, including that the system will be powered by solar panels.

Mr Musk will not be patenting the design and it will be “open source”, meaning anyone can modify it, or try to build it.

The fevered speculation about what it would actually look like has ranged from wild theories on Star Trek-style teleportation to more achievable ones involving cars being pushed through vacuum sealed tunnels using magnets.

Mr Musk has denied it will be a so-called “vactrain”, a concept that is already being pursued by a company in Colorado. His idea “does involve a tube, but not a vacuum tube”, he said, adding: “Not frictionless, but very low friction.”

In recent weeks a large part of the mystery appeared to have been solved. A technology enthusiast in Canada called John Gardi published a diagram of how the Hyperloop might work. He went on to ask Mr Musk on Twitter: “Can you give me some basic clues? What diameter of tube so I can start designing stations and throughways?”

To his extreme surprise Mr Musk replied: “Your guess is the closest I’ve seen anyone guess so far. Pod diameter probably around 2m.”

Mr Gardi, who describes himself modestly as a “tinkerer”, came up with a tunnel 9ft in diameter, raised above the ground on pylons. His tube could be made from materials already used for sewer pipes. It would form a continuous loop between two destination points. Giant turbines would blast a stream of air into the tube. The two-metre wide pods, carrying people, would be moved by a rail gun - a tube that uses magnets to accelerate material passing along it.

As they approach their journey’s end they would be routed out of the air stream and slowed down using a magnetic braking system.

In an extensive analysis published on the website Motherboard, Mr Gardi concluded: “I believe that Hyperloop is merely a modern day version of the pneumatic tubes used in banks, stores, and industry to move money and small items over long distances or to other floors of a building.

“They’ve been around for over a century, though not so much these days. One reason I think Hyperloop is simpler than folks think is that Elon Musk has resurrected another technology from the depths of time, one that was a contender once, too - the electric car!”

Mr Musk’s intended location for the first Hyperloop is California, between Los Angeles and San Francisco. His motivation for the project came from disillusionment with the Golden State’s high speed rail project, which has been dubbed the “bullet train to nowhere” after a series of setbacks.

He believes the Hyperloop could be built for a tenth of the cost and deliver passengers between the two cities in just 30 minutes, compared to three hours for the bullet train.

The bullet train is currently estimated to be costing $68 billion and may not be completed until 2028. It would reach top speeds of only around 130mph. In a survey seven in 10 people said, if the train ever does run, they would “never or hardly ever” use it anyway.

In an internet conversation this week with Sir Richard Branson, Mr Musk said: “I originally started thinking about it when I read a thing about California’s high speed rail project, which was somewhat disappointing. It is actually worse than taking the plane. I get a little sad when things are not getting better in the future.

“Another example would be like the Concorde being retired and the fact there is no supersonic passenger transport. I think that is sad. You want the future to be better than the past, or at least I do.

“The Hyperloop is something that would go effectively faster than the speed of sound. Conceivably you could live in San Fran and work in LA.”

Mr Musk said the Hyperloop would be best used between paired cities less than 1,000 miles apart, and would be safer than air travel.

However, Mr Musk said last week that he is too busy with space to build it himself. He added: “I think I kind of shot myself in the foot by ever mentioning the Hyperloop, because I’m too strung out. Obviously I have to focus on core Tesla business, and SpaceX business, and that’s more than enough.”

Mr Gardi has confidence though. He said: “Building Hyperloop’s main line for a tenth the cost of high speed rail is not only feasible, it’s doable.”